Abstract 2932: Knockdown of polypyrimidine tract-binding protein (PTB) sensitizes ovarian cancer cells to chemotherapeutic agents in vitro

Abstract

Abstract While chemotherapy is the second-line of therapy for the treatment of epithelial ovarian cancer (EOC) after surgery, drug resistance constitutes a significant obstacle to achieving a complete response in many patients. There is a clear unmet need for new treatments for EOC patients. We have shown that PTB is frequently overexpressed and associated with malignancy in EOC (He et al, Clin Cancer Res, 10:4652-60, 2004, He et al, Oncogene 30:356-65, 2011). PTB knockdown via RNA interference significantly impairs EOC cell growth in vitro and in vivo, as well as invasiveness and colony formation in soft agar in vitro (He et al, Oncogene 26:4961-8, 2007). PTB or hnRNP-I is a splicing factor that regulates alternative pre-mRNA splicing, and has been implicated in metabolic, cytoskeletal, and cell membrane changes in cancer cells. In this study, we used A2780 cell lines carrying doxycycline (doxy)-inducible PTB shRNA. We characterized stable transfectants of A2780 cells that carry shRNA against PTB and cells carry a non-targeting control shRNA. In a 48 h MTT cytotoxicity assay, knockdown of PTB inhibited cell growth. When cells with PTB knockdown were treated with carboplatin or paclitaxel, drugs used as current standard of care in EOC, we observed 3- to 6-fold increases in drug sensitivity compared to the vector control. To rule out any drug-drug interaction (e.g., doxy-paclitaxel) (Foroodi et al, Anticancer Drugs 2009 20:115-22) in our assay, we evaluated the kinetics of the inducible knockdown system by western blot. We found that a 120 h doxy treatment was optimal to insure full depletion of PTB, and after doxy removal PTB suppression lasted 48 h more before recovering to its basal level. Based on those data, we performed all the cytotoxicity experiments within 48 h without exposing cells to both doxy and drug at once, and thereby avoiding drug-drug interactions. Findings here support the idea that PTB and other splicing factors may be novel drug targets in the treatment of ovarian cancer. (Support in part by NCI grants R01 CA40570 and R01 CA138762 [to WTB], by OCRF [to XH], and by UIC.) Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 2932. doi:1538-7445.AM2012-2932